John Urschel plays a game in between the numbers, but off the football field, he dives deeper than that.

As most NFL players unlock the doors to their vacation homes during the off season, the Baltimore Ravens’ offensive lineman continues his work on a Ph. D. in applied mathematics at MIT.

Last year, in his first semester back at school in three years, Urschel earned four A’s in four Ph.D classes. His bedroom smells like chalk because he has a blackboard in there to work out math problems.

He was featured on this week’s episode of Real Sports on HBO, where he said the goal in math is “To understand. To learn. To push forward…It’s me versus this unknown.”

You might think making a seller block so his quarterback can throw a touchdown would be the best feeling in the world for an athlete like him, but that’s so far from the truth.

Check out this trailer.

So, the next time you think NFL players are only brawn, remember Urschel. He’s the guy issuing math challenges on The Players’ Tribune. He’s the guy who will be crushing math problems long after he’s done squashing linebackers.